Bolt going forward pulls the string which pulls the trigger. This is an old ruling from the BATFE. It makes the rounds every now and then because of the absurdity of registering a piece of string as a machine gun.

Sounds like it would work on any rifle that has a charging handle that moves with the bolt.

Imagine putting a screw in the right side of an AKM stock, tying one end of the string to the trigger, looping the string around the screw head and forward to the charging handle, so that the trigger is pulled when the bolt fully closes. Release the bolt and it would fire until it was empty... You could leave some slack in the string and then just pull the string to fire. I bet it'd work, but the question is why anyone would want to do that